In a semiconductor light emitting device such as a light emitting diode (LED) or a laser diode, a mounting material is used to fix a chip of a semiconductor light emitting element onto a lead or a substrate. As the mounting material, an epoxy-based resin may be used.
During a long time operation of a semiconductor light emitting device, an epoxy-based resin is heated by a light emitted from a chip of a semiconductor light emitting element and the color of the epoxy-based resin changes. The color change decreases reflection of light from the epoxy-base resin and decreases brightness. As a result, reliability of the semiconductor light emitting device is lowered.
As to a blue LED which generates light having a short wavelength and a high energy, the color change in an epoxy-based resin is accelerated, as compared with the other LEDs.